Todays GM vehicles use many sensor, switches, solenoids, and other electrical components to control or monitor every aspect of the engine.From controlling the fuel and ignition systems, to monitoring the emissions.A problem in any of these systems, or subsystems, can cause the check engine light to come on.

The first step in any diagnosis of the check engine light is to get the computer (PCM or ECM) scanned for codes. Any time this warning comes on, a code is stored in the computer memory along with many data parameters that were present at the time of the fault.

A simple code reader that can be purchased at any automotive supplier can retrieve these codes. Many of the large national parts store chains will scan the system at no charge. The code will give an indication as to what system has / had a problem. The more expensive scanners will also show live data, and allow further diagnosis by being able to control parts of a particular system.

The computer (PCM or ECM) is what controls the check engine light. You may have a bad computer or a shorted wire.

12-19-10Yes, I have the same issue on my 1996 Lesabre. Check Engine Lite and Traction Off... The car runs bad in town, but nice on the highway at 70 and above. Once warmed up it is allot better... Any recommendation

It could be any numbers of problems. Spark plug, plug wire, ignition coil, fuel injector etc. The fist step is to have the computer scanned for codes.

1-6-11i got code p0455 were is the problem

P0455 is for a large EVAP system leak. Either the gas cap is loose, not sealing, a line is leaking or you may have a vent or purge solenoid problem.

1-29-11i have a vehicle light with a wrench in middle want to know what this means.

Sounds like you are describing the "Service Vehicle" light. Either needs an oil change and get it reset, or a problem in an body system component and needs the Body controller scanned.

2-20-11would hollowing out a catalytic converter and the resonator i think its called then putting the o2 sensors back in them make the check engine light come on a 1998 Subaru ej25 motor

5-27-11sometimes my engine light blinks on and off when I'm driving but does not stay on

6-29-11I get regular oil changes and tune ups so the other day when my check engine light began flashing I didn't know what to think was wrong. It drives but when the car sits idle it feels as if it wants to shut off (It doesn't) it shakes just a little until i catch speed. I went to an auto parts store where he hooked it to a machine that read Cylinder 1 but then he sold me an ignition coil, spark plugs and wires???? I pray a simple coil replacement and tune up repair this problem. My friend had the same issue with his Lexus truck and that regimen worked for him. I pray it works for me as well.

The shaking you feel at idle is a cylinder that is misfiring. Usually it is ignition related, so a coil or new wires and plugs will most likely take care of it. It can at times be a fuel injector problem, so if your ignition repairs don't fix the problem, you should look into that.

6-30-11Thank you very much. I will try that

8-12-11I have a 2007 Chevy Impala and the check engine light came on. The repair shop said that i need a new secondary air pump and a control valve at a cost of appx. $700.00. He said this is an emission control problem. What damage does this do to the engine.

11-13-11i have an 01 Oldsmobile Alero that will not stay charged (battery) alternator good had checked check engine light on. Any ideas

This problem is called a parasitic draw. Something is staying powered on when the car is off and key is removed. You would need an amp meter and schematics to repair this. Removing fuses one at a time until draw goes away is a good start.

12-25-11Need help I have a 2005 Silverado on the dashboard have a light that reads a lock light what can I do it doesn't want to start.

This is the security warning light. the truck is in theft mode, that is why it won't start. You may have a bad ignition cylinder housing or ignition switch, of a faulty aftermarket remote start / alarm system if your truck has one.

i have a Chevy Trailblazer 2007 model , yesterday it all of a sudden stopped accelerating forward and not going in reverse. I switched off the car for some time. It starting moving forward and backwards. Can you tell me where is the problem. I had a mechanic look at it , he says the gears are all gone and i need a replacement .

Service engine soon light on. Will not scan on any code reader, just shuts them off

If the scanner shuts off, then either it is bad or the vehicle computer is bad or has a shorted wire.

I have a 1999 S-10 Pickup truck, Jan 09 it totalled stalled out with the Service Engine Light on spark plug wires, dist cap, rotor were all replaced, a year later water pump, hose assembly pump replaced, light still coming on and off at random, July 11 had all spark plug wires replaced dist cap, rotor etc replaced all this for $1500 and the dang light still pops on, truck runs with a little hesitation right before the light comes on and then it will just go out for no reason, doing nothing to make it go out, last suggestion was a new gas cap??? Any help would be great.

Your engine has a misfire. You need to get the codes scanned in the computer to even guess what may be wrong. One thing is for sure, it is NOT the gas cap!

What does it mean when temperature icon goes on? Also , overheating noticed. I put on my heat. (Which does not work) but, the temp gage did cool down ?

Code readers of any kind will not get the codes to flash. Even the manual jumper to get the codes to flash doesn't work. 94 S-10 V6 Vortec, new body style. In general the truck runs fine, but it bothers me that I can't read the codes. What is keeping the codes from being read?

If you cannot get the codes in any way, then you may either have a communication circuit problem between the computer and the diagnostic connector or a bad PCM. If it is a bad PCM, then it is just the a problem in that part of the computer, and will not cause any problems with the way your truck runs.

I have a 2004 Chevy Malibu. I got it checked and received a P0300 (random misfire). I have the coil packs, spark plugs and boots changed. One week after, my engine light came back on. It is not shaking like before. I am very disappointed as other place said the problem is the catalytic converter. I feel they should check the fuel injector, fuel pressure and a possible vacuum leak. I think that because of a random misfire, some unburned gas is now clogging the fuel injector. I am confuse and feel can't trust anybody to work on my car.

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